Prime Minister Ahmet Davutoglu made the surprise visit to the tomb of Suleyman Shah, grandfather of the Ottoman empire’s founder Osman I.

“Davutoglu’s infiltration into Syrian territory without the permission of the Syrian government constitutes a clear aggression against a sovereign UN member state and a violation of international law,” SANA said.

The tomb of Suleyman Shah, said to have died in 1236, is considered Turkish territory under the 1921 Treaty of Ankara between Turkey and France, which then controlled French-mandated Syria.

It was relocated from its previous site in February, in an unprecedented operation in which Turkish soldiers penetrated deep into Syria, also sparking a protest from Damascus.

The tomb is now just 200 metres (650 feet) from the Turkish border inside Syrian territory, in the settlement of Eshme which is easily visible from Turkey.

The visit comes amid speculation Turkey was preparing to intervene militarily in Syria, a claim rejected by Davutoglu.

SANA said the visit came in the “framework of election campaign propaganda” by Turkey’s ruling Justice and Development Party (AKP), which it said was facing “a significant decline in popularity” ahead of a June 7 parliamentary election.

Turkey has been a key backer of the uprising against Syria’s government, which accuses Ankara of supporting “terrorists”.